Apparatus for sewing fabrics



z 1966 J. c. CHEZAUD ETAL 3,241,503

APPARATUS FOR SEWING FABRICS Filed July 27, 1965 4 Sheets-Sheet 1 E nlors March 22, 1966 J, c, CHEZAUD ETAL 3,241,508

APPARATUS FOR SEWING FABRICS Filed July 27, 1965 4 Sheets-Sheet 2 Attorneys March 22, 1966 g, c z u ETAL 3,241,508

APPARATUS FOR SEWING FABRICS Filed July 27, 1965 4 Sheets-Sheet 5 V O) I X E k Y 7 3 L j b L Attorneys 3481111122, 1965 J. c. CHEZAUD ETAL 3,241,508

APPARATUS FOR SEWING FABRICS Filed July .27, 1965 4 Sheets-Sheet 4 Attorneys United States Patent 3,241,508 APPARATUS FOR SEWING FABRICS Jean Claude Chezaud, Chemin Fayolle, Saint-Rambertllle Barbe, France; Pierre Burillon, 60 Montee de lObservance, Lyon, France; and Dominique Mangieri, Cailloux-sur-Fontaine, France Filed July 27, 1965, Ser. No. 475,050 Claims priority, application France, Dec. 12, 1961,

2 Claims. in. 112 20s It has been proposed to use sewing machine needles which have a sharp edge facing upstream during the sewing, relative to the direction of advance of the fabric.

The ease with which the various fabric layers slide one upon the other causes irregularities in the stitches in addition to the puckering. In order to obviate this disadvantage, special machines have been designed which are provided with driving means which operate simultaneously on the top and bottom of the fabrics, or are even provided with means which drive the fabric by the needle.

A further difiiculty arises in the use of high-speed sewing machines with a thermoplastic thread, where the heating of the needle, due to friction with the fabric, sometimes causes melting and breaking of-the thread. In order to avoid these breakages, it is, for example, possible to fix on the sewing machine a device comprising a heated piercing needle which operates simultaneously with the sewing needle, so that the sewing needle enters the holes previously pierced by the heated needle disposed in front of it, the spacing between the piercing needle and the sewing needle being at least equal to the distance which separates two adjacent stitches.

However, if such a device is used, the heated needle, in piercing the fabric, carries with it small quantities of the material constituting the threads, this material being carbonized.

The present invention provides an apparatus which enables fabrics comprising thermoplastic threads to be sewn by the steps of (a) forming a series of equally spaced holes in said fabric along the line to be stitched by the passage of an electric spark through said fabric, and (b) sewing said fabric through said holes, continuously with their formation.

The apparatus of the invention comprises: a sewing machine having a presser foot; a stitching needle; a needle plate with an aperture for the passage of said stitching needle; means vertically reciprocating said stitching needle; fabric transport means, synchronized with said needle reciprocating means, effective to translate fabric stepwise from upstream of the needle plate aperture by a stitch length in each step when the stitching needle is in a position above the plane of passage of fabric through the machine; two electrodes; a high voltage supply; switch means operative to connect said high voltage supply to said electrodes; and spaced apart ends to the two electrodes defining a spark gap, said spark gap extending across the plane of passage of the fabric through the machine and being located upstream of the needle plate aperture at a distance therefrom of less than a stitch length, the switch means being synchronized with 3,241,508 Patented Mar. 22, 1966 the fabric transport means effective to connect said high voltage supply to said electrodes when the fabric transport means has, in its transport step, moved the fabric a distance equal to the difference between the stitch length and the distance of the spark gap from the needle plate aperture.

Preferably one of the electrodes is mounted in the presser foot and the other in the needle plate.

The discharge of sparks and the formation of the stitch are synchronized by an electrical switching device controlled by the driving shaft of the sewing machine, e.g. a centrifugal type of switch. Preferably there is also present means for switching off the supply of high voltage to the electrodes when necessary, for example when the machine is reversed, or when it is desired to utilize the machine as a conventional sewing machine.

It is desirable for the spark gap to be located as near as possible to the needle plate aperture, since the shorter the distance between the formation of the hole and passage of the stitching needle, the more accurately the hole can be positioned for the passage therethrough of the needle. If the holes are formed at a significant distance from the needle plate aperture, it is very difiicult to obtain a sufliciently accurate location of the fabric hole in relation to the needle plate aperture at the moment when the needle passes through.

A preferred embodiment of the invention is illustrated in the accompanying drawings, in which:

FIGURE 1 is a cross-section through the presser foot and the needle plate of the sewing machine,

FIGURE 2 is a diagram to show the relationship between the spark gap and the stitching needle,

FIGURE 3 is a plan view of the presser foot and needle plate,

FIGURE 4 is a schematic view of the sewing machine of the present invention, and

FIGURE 5 shows schematically the drive mechanism of the driving claws.

Referring now to FIGURE 1, a presser foot 1 and needle plate 2 contain two electrodes 3 and 4 insulated by a dielectric material 5. The straight line AB joining the tips of these two electrodes 3 and 4 intersects the sewing line on the fabric at point C at a small distance from the needle axis represented by line PG. The fabric is sewn by needle 7 and moved by driving claws 8.

In FIGURE 2 the line AB and the point C have the same significance as in FIGURE 1; line DE represents the seam line of the fabric and H is the projection of the needle axis FG of FIGURE 1.

When the needle 7 is raised and the driving claws 8 of the machine cause the fabric to move forward, a potential difference sufiiciently high to cause a spark discharge is set up between the two electrodes.

These sparks pass through the fabric and form a hole or line of weakness through the said fabric by melting or softening of the thermoplastic fibres in the zone traversed. The fabric is stopped by withdrawal of the claw and the needle 7 moves downwards passing through the hole thus formed, whereby a stitch is formed in conventional manner.

Referring to FIGURE 4, driving shaft 9 of a sewing machine 10 is driven by a motor 23, and imparts a vertical reciprocating movement to a needle shaft 11, to which is attached a stitching needle 7, by means of a connecting rod 12. The driving shaft 9 carries two cams, 13 and 14, which impart an up-and-down and to-and-fro movement to feed dogs 8 by means of conventional mechanical linkages 15 and 16. The relationship between the feed dogs 8, the cams 13 and 14 and the mechanical linkages 15 and 16 is shown in more detail in FIGURE 5. The driving shaft 9 carries also a cam 17 which engages with circuit breaker 18. The circuit breaker 18 makes and breaks a connection between conductors 19 and 20, conductor 19 being electrically connected to one terminal of a high tension source 21, and conductor 20 being electrically connected to an electrode 3 located in a presser foot 1. An electrode 4 is located in a needle plate 2 and electrically connected by conductor 22 to the other terminal of the high tension source 21, this connection being breakable by a switch 24 located between the electrode 4 and the terminal of the high tension source 21.

Thus the driving shaft 9 operates the stitching needle 7, the feed dogs 8 and the circuit breaker 18, and the relationship between the position of the stitching needle 7 and the passage of a spark between the electrodes 3 and 4 is controlled by the position of cam 17 relative to that of the connecting rod 12 and the circuit breaker 18. The position of the cam 17, or of the circuit breaker 18 is adjusted in accordance with the distance separating the spark gap between the electrodes and the needle plate aperture, so that a spark passes through the fabric before the needle passes through the presser foot, and the feed clogs bring the resultant hole in the fabric over the needle plate aperture at the moment the needle passes through the fabric. Exact location of the fabric hole when the needle passes through is facilitated by minimizing the distance between the formation of the hole, and the passage of the needle through it.

The diameter of the hole may most conveniently be regulated by varying the potential difference between the two electrodes. The invention is further illustrated by the following example.

Example Two pieces of fabric with a taffeta weave comprising threads consisting of polyamide 66 are fitted together by stitching and with a stitch length of 2 mm. on a sewing machine substantially as described. The distance between the axis of the needle and the plane parallel to this axis and passing through the straight line AB is 0.6 mm.

A needle having a diameter of 0.8 mm. is used, with a polyester sewing thread with a metric number of 70.

A current of 25 milliamperes at 10,000 volts is fed to the supply circuit of the electrodes to cause the spark discharge.

The stitching is carried out at a speed of 2,500 stitches per minute.

A seam without puckering is obtained, without breakage of the thread.

We claim:

1. Apparatus for sewing fabrics having thermoplastic threads comprising: a sewing machine having a presser foot; a stitching needle; a needle plate with an aperture for the passage of said stitching needle; means vertically reciprocating said stitching needle; fabric transport means, synchronized with said needle reciprocating means, effective to translate fabric stepwise from upstream of the needle plate aperture by a stitch length in each step when the stitching needle is in a position above the plane of passage of fabric through the machine; two electrodes a high voltage supply; switch means operative to connect said high voltage supply to said electrodes; and spaced apart ends to the two electrodes defining a spark gap, said spark gap extending across the plane of passage of the fabric through the machine and being located upstream of the needle plate aperture at a distance therefrom of less than a stitch length, a driving shaft operatively connected to the needle reciprocating means, the fabric transport means and the switch means; synchronizing means on said shaft effective to synchronize said fabric transport means with said needle reciprocating means and said switch means with said fabric transport means, a portion of said synchronizing means being effective to connect said high voltage supply to said electrodes when the fabric transport means has, in its transport step, moved the fabric a distance equal to the difference between the stitch length and the distance of the spark gap from the needle plate aperture.

2. Apparatus according to claim 1 including a mounting in the presser foot locating one electrode, and a mounting in the needle plate locating the other electrode.

No references cited.

JORDAN FRANKLIN, Primary Examiner.

R. J. SCANLAN, Assistant Examiner. 

1. APPARATUS FOR SEWING FABRICS HAVING THERMOPLASTIC THREADS COMPRISING: A SEWING MACHINE HAVING A PRESSER FOOT; A STITCHING NEEDLE; A NEEDLE PLATE WITH AN APERTURE FOR THE PASSAGE OF SAID STITCHING NEELDE; MEANS VERTICALLY RECIPROCATING SAID STITCHING NEEDLE; FABRIC TRANSPORT MEANS, SYNCHRONIZED WITH SAID NEEDLE RECIPROCATING MEANS, EFFECTIVE TO TRANSLATE FABRIC STEPWISE FROM UPSTREAM OF THE NEEDLE PLATE APERTURE BY A STITCH LENGTH IN EACH STEP WHEN THE STITCHING NEEDLE IS IN A POSITION ABOUT THE PLANE OF PASSAGE OF FABRIC THROUGH THE MACHINE; TWO ELECTRODES A HIGH VOLTAGE SUPPLY; SWITCH MEANS OPERATIVE TO CONNECT SAID HIGH VOLTAGE SUPPLY TO SAID ELECTRODES; AND SPACED APART ENDS TO THE TWO ELECTRODES DEFINING A SPARK CAP, SAID SPARK GAP EXTENDING ACROSS THE PLANE OF PASSAGE OF THE FABRIC THROUGH THE MACHINE AND BEING LOCATED UPSTREAM OF THE NEEDLE PLATE APERTURE AT A DISTANCE THEREFROM OF LESS THAN A STITCH LENGTH, A DRIVING SHAFT OPERATIVELY CONNECTED TO THE NEEDLE RECIPROCATING MEANS, THE FABRIC TRANSPORT MEANS AND THE SWITCH MEANS; SYNCHRONIZING MEANS ON SAID SHAFT EFFECTIVE TO SYNCHRONIZE SAID FABRIC TRANSPORT MEANS WITH SAID NEEDLE RECIPROCATING MEANS AND SAID SWITCH MEANS WITH SAID FABRIC TRANSPORT MEANS, A PORTION OF SAID SYNCHRONIZING MEANS BEING EFFECTIVE TO CONNECT SAID HIGH VOLTAGE SUPPLY TO SAID ELECTRODES WHEN THE FABRIC TRANSPORT MEANS HAS, IN ITS TRANSPORT STEP, MOVED THE FABRIC A DISTANCE EQUAL TO THE DIFFERENCE BETWEEN THE STITCH LENGTH AND THE DISTANCE OF THE SPARK GAP FROM THE NEEDLE PLATE APERTURE. 